test0r
fc4bb1063f
The H.264 stateless control structs and CIDs were upstreamed and
reshaped during the journey from libva-v4l2-request's bundled headers
to the kernel's <linux/v4l2-controls.h>. Three breaking changes need
matching code-side updates:
1. struct v4l2_ctrl_h264_slice_params lost its .size field. The full
slice byte length is now communicated via the OUTPUT buffer's
m.planes[0].bytesused at QBUF time, which v4l2_queue_buffer already
sets. Drop the assignment.
2. struct v4l2_h264_reference replaces the bare integer DPB index in
ref_pic_list0[] / ref_pic_list1[]. The new struct is { __u8 fields,
__u8 index } where `fields` is V4L2_H264_TOP_FIELD_REF (0x1) /
BOTTOM_FIELD_REF (0x2) / FRAME_REF (0x3). Hantro G1 only does
frame-based H.264, so use V4L2_H264_FRAME_REF unconditionally.
3. The pred_weight_table block moved out of slice_params into its own
V4L2_CID_STATELESS_H264_PRED_WEIGHTS control with struct
v4l2_ctrl_h264_pred_weights. Add it as a separate v4l2_set_control()
call alongside SPS/PPS/SLICE_PARAMS/DECODE_PARAMS/SCALING_MATRIX, and
thread the pred_weights pointer through h264_va_slice_to_v4l2().
Also: switch the v4l2_set_control() CID arguments from V4L2_CID_MPEG_VIDEO_H264_*
to V4L2_CID_STATELESS_H264_* directly. h264-ctrls.h still defines the
old names as aliases so external callers keep working, but using the
canonical names internally matches what the kernel actually expects and
avoids confusion when reading h264.c side-by-side with the kernel
source.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
v4l2-request libVA Backend
About
This libVA backend is designed to work with the Linux Video4Linux2 Request API that is used by a number of video codecs drivers, including the Video Engine found in most Allwinner SoCs.
Status
The v4l2-request libVA backend currently supports the following formats:
- MPEG2 (Simple and Main profiles)
- H264 (Baseline, Main and High profiles)
- H265 (Main profile)
Instructions
In order to use this libVA backend, the v4l2_request driver has to
be specified through the LIBVA_DRIVER_NAME environment variable, as
such:
export LIBVA_DRIVER_NAME=v4l2_request
A media player that supports VAAPI (such as VLC) can then be used to decode a video in a supported format:
vlc path/to/video.mpg
Sample media files can be obtained from:
http://samplemedia.linaro.org/MPEG2/
http://samplemedia.linaro.org/MPEG4/SVT/
Technical Notes
Surface
A Surface is an internal data structure never handled by the VA's user containing the output of a rendering. Usualy, a bunch of surfaces are created at the begining of decoding and they are then used alternatively. When created, a surface is assigned a corresponding v4l capture buffer and it is kept until the end of decoding. Syncing a surface waits for the v4l buffer to be available and then dequeue it.
Note: since a Surface is kept private from the VA's user, it can ask to directly render a Surface on screen in an X Drawable. Some kind of implementation is available in PutSurface but this is only for development purpose.
Context
A Context is a global data structure used for rendering a video of a certain format. When a context is created, input buffers are created and v4l's output (which is the compressed data input queue, since capture is the real output) format is set.
Picture
A Picture is an encoded input frame made of several buffers. A single input can contain slice data, headers and IQ matrix. Each Picture is assigned a request ID when created and each corresponding buffer might be turned into a v4l buffers or extended control when rendered. Finally they are submitted to kernel space when reaching EndPicture.
The real rendering is done in EndPicture instead of RenderPicture because the v4l2 driver expects to have the full corresponding extended control when a buffer is queued and we don't know in which order the different RenderPicture will be called.
Image
An Image is a standard data structure containing rendered frames in a usable pixel format. Here we only use NV12 buffers which are converted from sunxi's proprietary tiled pixel format with tiled_yuv when deriving an Image from a Surface.